Ryan Baird and Charlie Tector have been ruled out of Leinster's Champions Cup semi-final with Toulon on Saturday at Aviva Stadium, while doubts remain over a number of players including Tadhg Furlong and Andrew Porter.
In a boost for the province, James Lowe is back in training and could yet feature.
Lowe, along with Diarmuid Mangan and Jordan Larmour, are back on the grass and need further checks to see if they could play against the French outfit.
Furlong was injured in Saturday’s URC loss against Benetton and his absence would compound their prop woes.
Speaking to RTÉ Sport, Leinster assistant coach Robin McBryde said that they would make a final decision later in the week.
"It's tough isn't it when you've got a history of injuries? Alarm bells are going to ring pretty quickly at the slightest feel of anything," he said.
"We're going to have to assess that and he see how he goes. Hopefully it'll be nothing too bad."
Porter has been out since the Champions Cup clash with Edinburgh at the start of this month, with Leinster giving him every opportunity to prove his fitness this weekend.
Paddy McCarthy, Jack Boyle, RG Snyman and Alex Usanov are not in contention.
Leo Cullen’s side have been plagued by injuries in recent months as they face the crunch last four clash.
Ulster, meanwhile, have said that Callum Reid and Ben Carson have been ruled out of Saturday's Challenge Cup semi-final against Exeter Chiefs in Belfast.
Reid picked up a foot injury against Munster in Saturday’s URC and Carson hurt his calf, ensuring both miss out. Eric O’Sullivan suffered a back injury in the same game and is being assessed.
Tom O'Toole (hand), Nick Timoney (hip) and Jude Postlethwaite (hand) have all returned from injury though and are available for selection. Angus Bell (foot), James Hume (neck), and Bryn Ward (shoulder) could also be in contention for returns, but no decision has been made yet on the trio.
